JP3020380B2 - Thermal transfer recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording medium having a release layer between a substrate and a hot-melt colored ink layer.

[0002]

2. Description of the Related Art Conventionally, a thermal transfer recording medium capable of forming an image of good quality even on paper having a poor surface smoothness (hereinafter referred to as rough paper) has generally been used in a cross-linkable medium. (Hereinafter referred to as an ink layer transferred so as to bridge a concave portion of rough paper). In order to obtain such a heat-fusible ink layer having a strong cross-linking property, usually, a heat-fusible vehicle of an ink mainly composed of a resin and having a large cohesive force is used.

[0003] Further, since thermal printing recording media for label printing, such as bar code labels, also require robustness of printing, similarly, a heat-fusible vehicle mainly made of resin and having a large cohesive force is used. .

However, in the case where such a vehicle is a hot-melt ink layer mainly composed of a resin, the adhesion between the vehicle and a substrate when heated by a heating head and then peeled off from a receiving paper during printing is reduced. The transfer is not performed favorably because of its large size and poor releasability from the substrate.

Therefore, a means for improving transferability by providing a release layer having a low melt viscosity mainly composed of wax between the hot-melt colored ink layer and the base material has been taken.

However, if a release layer having a low melt viscosity is used to improve the releasability of the ink layer from the substrate during printing, the following problems occur.

(1) The so-called ink powder phenomena, in which the adhesion to the substrate in a non-heated state before printing is reduced, and the ink layer is peeled off from the substrate in a powder form even by a small physical action such as rubbing. Occurs.

(2) Since the adhesive force between the release layer and the ink layer is weakened, the unheated portion of the ink layer is separated from the release layer along with the adjacent heating portion, so-called planar peeling ( Of the statue,
As a result, the ink is stained as if the tail was moved in the direction opposite to the moving direction of the heating head.

If the melt viscosity of the release layer is increased in order to avoid the above-mentioned problems, the releasability at the time of transfer is deteriorated, the meaning of providing the release layer is lost, and the base material is not removed at the time of release from the receiving paper. Since a large force is applied to the material, wrinkles are generated on the base material, and the ribbon winding side becomes thicker or dislocated on the winding side of the ribbon, which also causes a running failure of the ribbon and a lack of printing.

On the other hand, Japanese Patent Application Laid-Open No. 61-268485 discloses a technique in which a fine powder layer is provided between a substrate and an ink layer in order to improve releasability. However, since this fine powder layer does not contain a heat-fusible binder component such as wax, the adhesion to the substrate is inferior, and the above-mentioned powder dropping phenomenon is likely to occur. For example, when the adhesion to the substrate is increased by increasing the drying temperature during coating, there is a disadvantage in that the releasability during transfer deteriorates.

In view of the foregoing, the present invention provides a mold release which has a high adhesion to a substrate in a non-heated state before printing, and has a good releasability of a heated portion from the substrate during peeling during printing. It is an object of the present invention to provide a thermal transfer recording medium in which a layer is developed so that defects such as powder dropping and tailing do not occur.

[0012]

The present invention provides a thermal transfer recording medium comprising a heat-meltable release layer and a heat-meltable colored ink layer laminated on a substrate in this order. The layer is formed by applying particles having a mean particle diameter of 1 to 6 μm and containing a wax-like substance as a main component at a coating amount of 0.3 to 2.5 g / m ² , and the average particle diameter and the coating amount of the particles are determined. 0.28R ≦ M ≦ 0.83R (wherein, R is the value of the average particle diameter of the particles expressed in units of μm, and M is the value of the amount of coating expressed in units of g / m ² ) The present invention relates to a thermal transfer recording medium having the following relationship:

[0013]

In the present invention, since the release layer is composed of particles containing a wax-like substance as a main component, the releasability of the heated portion during printing is improved. Further, a structure in which the ink of the hot-melt colored ink layer passes through the particles of the release layer and is in contact with the base material by satisfying the average particle diameter of the particles, the coating amount and the relationship between the two ranges. Therefore, the adhesion between the ink layer and the base material in a non-heated state is large, so that powder drop does not occur. In addition, since the adhesive force between the ink layer and the release layer is large, planar separation does not occur. In addition, since it has good releasability at the time of heat transfer, a large force is not applied to the substrate at the time of release from the receptor, and no wrinkles are generated on the substrate.

The reason why planar separation does not occur when the adhesion between the ink layer and the release layer is large is as follows. That is, when the recording medium is peeled off from the receptor after heating by the heating head, the interface shear force between the heated portion and the non-heated portion in the ink layer is F1, and the adhesion force between the release layer and the ink layer in the non-heated portion is F1. When F2 is satisfied, when F2 <F1, the heated portion is peeled off with the surrounding non-heated portion.
When F1 <F2, the ink layer breaks at the boundary between the heated portion and the non-heated portion, so that no planar separation occurs.

As described above, the release layer of the present invention has a feature that the adhesive force with the substrate is large in the non-heated state before printing, but the adhesive force with the substrate is small in the heated state during printing. However, in the release layer composed of only fine powder described in JP-A-61-268485, a large difference is created in the adhesion between the non-heated state and the heated state with the base material. Can not.

Next, the present invention will be specifically described.

The release layer in the present invention is formed by particles containing a wax-like substance as a main component.

Examples of the waxy substance include natural waxes such as wood wax, beeswax, carnauba wax, candelilla wax, montan wax and ceresin wax; petroleum waxes such as paraffin wax and microcrystalline wax; oxidized waxes and esters Synthetic waxes such as wax, polyethylene wax, Fischer-Tropsch wax, α-olefin-maleic anhydride copolymerized wax; higher fatty acids such as myristic acid, palmitic acid, stearic acid and behenic acid; higher aliphatic alcohols such as stearyl alcohol and docosanol Esters of higher fatty acid monoglyceride, fatty acid ester of sucrose, fatty acid ester of sorbitan and the like; amides such as stearamide, oleylamide and bisamide One or more, such as can be used.

Among them, those having a low melt viscosity are preferred. Examples of such waxy substances include carnauba wax, candelilla wax, montan wax, paraffin wax, ester wax, Fischer-Tropsch wax and the like.

The melting point or softening point of the wax-like substance is preferably set to about 50 to 130 ° C. under ordinary transfer conditions. The melt viscosity varies depending on the transfer conditions and the like and cannot be unconditionally determined. However, it is usually preferable that the melt viscosity be 1000 cps or less at a temperature 30 ° C. higher than the melting point or the softening point, and 100 cps or less.

The waxy substance has an average particle size of 1 to 6.
μm is preferred. If the average particle diameter is less than 1 μm, the state becomes close to a continuous layer, and the ink retainability during non-heating and the ink releasability during heat transfer tend not to be exhibited. On the other hand, when the average particle diameter exceeds 6 μm, the thickness of the release layer becomes too large, so that the heat conduction becomes poor and the transferability tends to decrease.

The coating amount (the coating amount after drying, the same applies hereinafter) of the particles containing the wax-like substance as the main component of the release layer is 0.3 to 2.
A range of 5 g / m ² is preferred. If the coating amount is less than the above range, the peeling effect is poor, and if it is more than the above range, the thermal diffusion increases, which is not preferable.

Further, the coating amount of the particles in the release layer is preferably changed according to the average particle diameter. That is, as the average particle diameter becomes smaller, the coating amount is reduced,
Mean particle size R and g of said particles expressed in μm units
It is preferable that the value of the coating amount expressed in the unit of / m ² has a relationship of 0.28R ≦ M ≦ 0.83R.

When the average particle diameter and the coating amount of the particles mainly composed of the wax-like substance and the relationship between the two satisfy the above ranges, the ink in the ink layer passes through the gaps between the particles and is applied to the substrate. To achieve an anchoring effect.

The release layer is obtained by applying a solvent dispersion, an emulsion or the like of particles containing a wax-like substance as a main component on a substrate and drying the resultant. The drying temperature is such that the particles melt,
A temperature that does not dissolve. In preparing the solution dispersion and the emulsion, a surfactant may be used.
Examples of aqueous surfactants include alkyl sulfates, alkyl benzene sulfonates, higher fatty acid salts, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, naphthalene sulfonate formalin condensates, polyoxyethylene alkyl sulfates, alkyl Amine salts and the like. Other cationic surfactants,
An anionic surfactant, a nonionic surfactant, or the like may be used. If necessary, a heat-fusible resin of 20% by weight or less of the release layer may be used as a binder.

As the hot-melt colored ink layer in the present invention, a conventional colored ink layer having a high melt viscosity can be used without any particular limitation.

For example, there may be mentioned a composition in which a colorant and a high-melting-viscosity hot-melt vehicle are used as main components, and if necessary, a dispersant, an extender and the like are added. Examples of the heat-meltable vehicle having a high melt viscosity include those mainly containing a heat-meltable resin and, if necessary, a wax-like substance.

The softening point of the ink layer is preferably about 50 to 170 ° C., and the melt viscosity is 10 ³ to 10 ^{9 at a} temperature 30 ° C. higher than the softening point.
It is preferably about cps.

Examples of the heat-fusible resin include olefin copolymer resins such as ethylene-vinyl acetate copolymer and ethylene-acrylate copolymer, polyamide resin, polyester resin, epoxy resin, and polyurethane resin. Resin, acrylic resin, vinyl chloride resin,
Cellulose resin, vinyl alcohol resin, petroleum resin, phenol resin, styrene resin, vinyl acetate resin, natural rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber and other elastomers, polyisobutylene, polybutene, etc. One or more kinds may be mentioned.

As the wax-like substance, those exemplified for the release layer can be used.

As the colorant, any of those conventionally used as colorants for this type of hot-melt ink can be used.
Various organic pigments and dyes are appropriately used. The content of the colorant in the ink layer is usually about 10 to 50%.

The hot-melt colored ink layer is formed by applying a coating liquid obtained by dissolving and dispersing the above-mentioned ink component in a solvent (which does not substantially dissolve particles of a wax-like substance) onto a release layer, It is formed by drying at a temperature at which the wax-like substance particles do not melt and dissolve. The amount of ink layer applied is 0.
About 5 to 6 g / m ² is appropriate.

Examples of the substrate in the present invention include polyester films such as polyethylene terephthalate film and polyethylene naphthalate film, polycarbonate films, polyamide films, aramid films, and the like.
In addition, various plastic films generally used as a film for a substrate of this type of ink ribbon can be used. Also, high-density thin paper such as condenser paper may be used. The thickness of the substrate is preferably about 1 to 10 μm, particularly preferably about 2 to 7 μm, from the viewpoint of improving heat conduction.

When the above-mentioned plastic film is used as the base material, a silicone resin, a fluororesin, a nitrocellulose resin, or a silicone-modified acrylic resin modified with these, for example, on the back surface (the surface on the side in contact with the heating head). Various kinds of lubricating heat-resistant resin,
Alternatively, a conventionally known stick preventing layer made of a mixture of a heat-resistant resin and a lubricant may be provided.

Next, the present invention will be described with reference to examples.

Examples 1-2 and Comparative Examples 1-2 A 3.5 μm thick polyethylene terephthalate film having a silicone-modified acrylic resin layer having a thickness of 0.1 μm formed on the back surface was used for the release layer shown in Table 1. 10 parts by weight of the wax-like substance was added to 90 parts by weight of toluene together with a surfactant, heated and dissolved once, then cooled to precipitate wax particles, and the wax dispersion thus obtained was applied. It dried at ° C and formed a release layer. In Comparative Example 1, the same wax as in Example 1 was applied as a continuous layer by a hot melt coating method at an application amount of 1.0 g / m ² ,
In Comparative Example 2, a methanol dispersion of colloidal silica was used in 1.
0 g / m ^{2 was} applied and dried.

[0037]

[Table 1]

Next, a coating liquid for an ink layer shown below was applied on the release layer and dried at 50 ° C. to apply 2.0 g /
m ² , softening point 110 ° C, melt viscosity 3 × 10 ⁷ cps / 140 ° C
Was formed.

Coating solution for ink layer Component parts by weight Ethylene-vinyl acetate copolymer resin (softening point 60 ° C.) 10 Carbon black 8 Porous silica powder (average particle size 4 μm) 2 Toluene 30 Methyl ethyl ketone 50 Using each thermal transfer recording medium, a serial thermal transfer printer manufactured by NEC Corporation, PC-PR150V
A printing test was performed to evaluate the following items. Xerox 4024 (Beck smoothness 28 seconds) was used as the receiving paper. Table 2 shows the results.

(1) Transferability Printing was performed at the maximum output (0.1 mJ / dot) of the printer, and the reflection density (OD value) of the printing obtained on the receiving paper was measured.
Evaluation was made according to the following criteria.

3 ... OD value of 1.5 or more.

2: OD value 1.0 or more and less than 1.5.

1 ... OD value is less than 1.0.

(2) Powder Fall After printing under the same conditions as above, the state of peeling of the ink layer from the base material in the unused portion was observed and evaluated according to the following criteria.

3: No lifting or peeling of the ink layer from the substrate is observed.

2: Floating of the ink layer from the substrate is observed.

1. Peeling of the ink layer from the substrate is observed.

(3) Planar separation Printing was performed under the same conditions as above, and an enlarged photograph (25
Times), and observe whether or not planar separation has occurred.
Evaluation was made according to the following criteria.

2: No planar peeling occurred.

1 ... Surface peeling has occurred.

[0051]

[Table 2]

[0052]

The release layer provided between the base material and the colored ink layer has a coating amount of the wax-like substance having an average particle diameter of 1 to 6 μm of 0.3 to 2.5 g / m ^2. By having the above-mentioned specific relationship between the particle diameter and the coating amount, the adhesion between the ink layer and the base material in a non-heated state is large, so that the powder does not fall off, and the adhesion between the ink layer and the release layer. Is large, so that surface peeling does not occur. In addition, since it has good releasability at the time of heat transfer, a large force is not applied to the substrate at the time of peeling from the receptor, and no wrinkles are generated on the substrate.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 31/04 B41M 5/30

Claims (1)

(57) [Claims] 1. A thermal transfer recording medium comprising a heat-meltable release layer and a heat-meltable colored ink layer laminated on a substrate in this order, wherein the heat-meltable release layer has an average particle diameter of 1 to 1. 6μ
Amount of particles whose main component is waxy substance in the range of m
0.3 to 2.5 are those coated with a range of g / m ^2, and 0.28R ≦ M ≦ 0.83R (wherein, R between the average particle diameter and coating amount of the particles expressed in units of μm And M represents the value of the coating amount expressed in units of g / m ² ).